Credit

Caption

Halo, arcs and sun dogs. Sun (lower centre) and caused by ice crystals in the atmosphere. This is a 22-degree halo, with sun dogs (parhelia) visible as the bright spots on each side of the halo. Three arcs are also visible: a faint one on top of the halo (an upper tangent arc), and two rainbow-like ones at top (a supralateral arc and a circumzenithal arc). These phenomena were observed from Pitea in Sweden, on 4 October 1839. Artwork from 'Cours complete de meteorologie' (1843) by German physicist and meteorologist Ludwig Friedrich Kaemtz (1801-1867).